(1) Field of the Invention
The present invention relates to a repair coating method applicable to an automobile body, a railway vehicle, an industrial equipment, woodworking, etc., and capable of providing good finish in a very short period of time.
(2) Description of the Background Art
The repair coating of the automobile body, etc. is carried out in the art by a coating process which comprises removing an old coating film in a damaged area, applying a putty composition onto the old coating film-removed area, drying, sanding the putty-applied surface, coating thereonto a primer coating composition, sanding, coating a topcoat, and coating a clear coat for finishing.
The repair coating method in the art is such that a cold-setting, two pack type, an unsaturated group-containing polyester resin-based coating composition is used in the putty-applied layer, and a two pack type, acrylic urethane based coating composition is used in the primer layer and clear layer by means of air-drying or force-drying by use of a hot-air, and curing after coating step takes 20 minutes to one hour at 60xc2x0 C., resulting in producing such problems that repair steps take as a whole a long period of time.
The present inventors made intensive studies on solving the above problems in the prior art to find out that the use of a one pack type photocurable composition in the substrate processing and the use of a photocurable composition in the clear layer makes it possible to remarkably shorten a total time taken in respective repair steps, and to form a coating film showing good properties in hardness, interlayer adhesion properties, finish properties, and the like, resulting in accomplishing the present invention.
It is an object of the present invention to provide a repair coating method capable of remarkably shortening a total time taken in respective repair steps, and forming a coating film showing excellent coating film performances.
That is, the present invention provides the following repair coating methods (1) to (6).
(1) A repair coating method which comprises coating a photocurable processing composition (I) onto a damaged area of a substrate to form a processed layer, followed by coating a colored base coating composition (II) onto the processed layer to form a colored base layer, and coating a photocurable clear composition (III) onto the colored base layer to form a clear layer.
(2) A repair coating method according to the above method (1), wherein the processed layer formed from the photocurable processing composition (I) is formed from a photocurable putty composition (I-1) containing a polymerizable unsaturated group-containing resin, a polymerizable unsaturated compound and a photopolymerization initiator.
(3) A repair coating method according to the above method (1), wherein the processed layer formed from the photocurable processing composition (I) is a multi-coating film layer comprising a coating film formed from the photocurable putty composition (I-1) and a coating film formed from a photocurable primer composition (I-2).
(4) A repair coating method according to the above method (3), wherein the method comprises coating the photocurable putty composition (I-1) onto the damaged area of the substrate to form a putty layer, coating the photocurable primer composition (I-2) onto the putty layer to form a primer layer, irradiating light to cure both layers simultaneously, coating the colored base coating composition (II) to form a colored base layer, coating the photocurable clear composition (III) to form a clear layer, and irradiating light to cure both layers simultaneously.
(5) A repair coating method according to the above method (3) or (4), wherein the photocurable putty composition (I-1) has a pigment volume concentration in the range of 10 to 30%, and the photocurable primer composition (I-2) has a pigment volume concentration in the range of 10 to 40%.
(6) A repair coating method according to the above method (3), (4) or (5), wherein the photocurable primer composition (I-2) contains (A) an acrylic resin having through an urethane linkage a polymerizable unsaturated group on its side chain, (B) an urethane (meth)acrylate oligomer containing at least one polymerizable unsaturated group in one molecule, and a photopolymerization initiator.